Product category:
Industrial Drives/Controls
News Release from: Rockwell Automation | Subject: 12-pulse inverters
Edited by the Engineeringtalk Editorial
Team on 17 August 2001
Drives play a part in meeting G5/4
recommendations
Rockwell Automation is supplying 12-pulse inverters to users of variable speed drives, enabling them to keep harmonic distortion within the guidelines of Engineering Recommendation G5/4
Rockwell Automation is supplying 12-pulse inverters to users of variable speed drives, enabling them to keep harmonic distortion within the limits of Engineering Recommendation G5/4 G5/4 contains recommendations for maximum harmonic distortion to electrical supplies in the UK
This article was originally published on Engineeringtalk on 20 Feb 2001 at 8.00am (UK)
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It supersedes the well-established G5/3, setting new, tougher restrictions on harmonic voltage distortion and connection of non-linear loads to the supply system.
These more stringent recommendations can result in low voltage 6-pulse inverters greater than approximately 40kW no longer being suitable for direct connection to the National Grid electrical supply.
Most off-the-shelf, low voltage AC variable speed drives use 6-pulse inverters, which under the old G5/3 standard would have been acceptable up to power ratings of around 75kW.
Rockwell Automation's drives engineering facility at Bletchley builds inverters using isolating phase shifting transformer and series rectifier bridges into standard 6-pulse units, converting them to true 12-pulse drives.
This vastly reduces the key 5th and 7th harmonics generated by 6-pulse drives, which cause the biggest problems to the Grid.
Rockwell Automation is able to design and supply 12-pulse drives in ratings up to 600kW within six to eight weeks of receiving an order.
One alternative to 12-pulse drives is to use an active harmonic filter to reduce the harmonics put in to the mains by a 6-pulse drive.
Rockwell Automation believes however that the most cost effective route to meeting G5/4 recommendations is to install true 12-pulse technology.
Orders for 12-pulse systems have already increased following the publication of G5/4, and Rockwell Automation recently supplied a 160kW 12-pulse drive for use in a pumping station.
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